1. Field of the Invention
The present invention relates to a vehicle lamp and a vehicle lamp unit for irradiating a light beam forward under a predetermined light distribution pattern.
2. Prior Art
Generally, a headlamp for a vehicle is structured to irradiate light beam forward with a light distribution pattern that varies in accordance with a vehicle driving state. In other words, a conventionally known headlamp is switchable between the low beam light distribution pattern and the high beam light distribution pattern.
When a vehicle runs on the road in a wet condition in the rain, most of the forward irradiation light from the headlamp is reflected regularly on the road surface. This may reduce the reflective intensity light to the driver, thus deteriorating visibility with respect to the road surface forward of the vehicle, and hindering the driver from driving in good condition.
Generally, lane marks (i.e., a white line partitioning the vehicle lanes) are painted on a paved road. It is visible even on the wet road surface. Therefore, if the forward irradiation light amount from the headlamp is increased, it is possible to enhance the visibility of the lane marks, thus facilitating driving correspondingly.
However, the increase in the amount of the forward irradiation light from the headlamp emits glare to the driver of an oncoming vehicle. This may hinder the driver of the oncoming vehicle from driving in an appropriate condition.
Japanese Patent Application Laid-open (Kokai) No. H5-338487 discloses a vehicle lighting unit in which a forward road surface of a running vehicle is imaged, and the image is processed to detect the position of the lane marks. Then, an optical axis of the headlamp is turned to the direction of the lane marks based on the detection result. Such an apparatus may enhance the visibility with respect to the lane marks. However, glare to a driver of the oncoming vehicle cannot be reduced. In addition, the structure of such an apparatus is extremely complicated.
The present invention solves the foregoing problems.
The object of the invention to provide a vehicle lamp and a vehicle lamp unit capable of enhancing a visibility of a forward road surface of a vehicle in the rain without applying emitting glare to the driver of the oncoming vehicle.
The above object is accomplished by a unique structure for a vehicle lamp that irradiates a light beam forward that has a light distribution pattern suitable for irradiating the lane marks.
More specifically, the present invention provides a vehicle lamp for irradiating a light beam forward with a predetermined light distribution pattern; and in the present invention, the luminous intensity distribution in lateral direction in a first angle position which is a downward direction at a predetermined angle with respect to a longitudinal axis passing through a center of the lamp of the light distribution pattern is set to be a luminous intensity distribution that has a pair of left and right peaks relative to the longitudinal axis.
In an actual vehicle, the xe2x80x9cvehicle lampxe2x80x9d is used with a normal headlamp (i.e., headlamp switchable between a low beam and a high beam). The vehicle lamp may be turned ON while turning the headlamp ON. Only the vehicle lamp may be turned ON instead.
The specific lamp structure for the xe2x80x9cluminous intensity distribution having a pair of left and right peaks of an axis in the longitudinal directionxe2x80x9d is not particularly limited. For example, it is possible to employ a structure in which the light from a light source is controlled to permeate and is deflected by a reflector. In addition, a structure in which the light incident from the light source to the reflector is controlled to be partially shaded by a shade can be employed; and a structure that is a combination of the above-described structures can be also employed as well.
As seen from the above, the vehicle lamp of the present invention irradiates a light beam forward with a predetermined light distribution pattern, and the luminous intensity distribution in lateral direction in a first angle position which is downward direction at a predetermined angle with respect to a longitudinal axis passing through the center of the lamp of the light distribution pattern is set so as to be a luminous intensity distribution that has a pair of (left and right) peaks relative to the longitudinal axis. Accordingly, it is possible to increase the irradiation light amount to the left and right regions while restricting the irradiation light amount to a front region of the light of the road surface ahead of the vehicle corresponding to the first angle position.
Therefore, when the road surface is wet in the rain, for instance, it is possible in the present invention to prevent emission of the great glare to a driver of an oncoming vehicle by regular reflection on the front region of the lamp of the road surface ahead of the vehicle, and it is also possible to brightly irradiate the lane marks existing on the left and right regions.
According to the present invention, the visibility with respect to the forward road surface of a vehicle driving in the rain is enhanced without emitting the great glare to the driver of the oncoming vehicle.
The downward angle with respect to the longitudinal axis of the xe2x80x9cfirst angle positionxe2x80x9d is not limited. Assuming that it is set to 4xc2x0 and the height of the lamp unit from the ground to its center is 0.7 m, such a position corresponds to the point on the road surface ahead of the vehicle about 10 m forward from the headlamp. When the light beam irradiated to the point in the close forward region of about 10 m normally reflects in the front region of the lamp, the light beam emits great glare to the driver of the oncoming vehicle. The light beam, however, is suitable for irradiating the lane marks on the left and right side of the region. Therefore, it is especially effective to set the first angle position to the point inclined downward at 4xc2x0 for providing the effect.
In the above-described structure, furthermore, the luminous intensity distribution of the light distribution pattern in lateral direction in a second angle position which is downward direction at a predetermined angle with respect to the first angle position is set to a luminous intensity distribution that has a pair of left and right peaks relative to the longitudinal axis, and the pair of peaks of the second angle position are located at position away from the longitudinal axis with respect to the pair of peaks in the first angle position. This arrangement provides the following effects.
Suppose that the road surface ahead of the vehicle is viewed from the vehicle lamp, the lane marks appear to extend radially from the lamp""s longitudinal axis to the lower left and the lower right directions. Therefore, if the peaks of the second angle position are located away from the longitudinal axis with respect to those peaks in the first angle position, the light distribution pattern extending radially from the longitudinal axis to the lower left and the lower right can be obtained. This makes it possible to irradiate the road surface ahead of the vehicle brightly along the lane marks.
If, for example, the second angle position is set to be inclined downward at 8xc2x0 and the height from the ground to the center of the lamp is 0.7 m, then such a position corresponds the point on the road surface ahead of the vehicle about 5 m from the lamp. As a result, the lane marks are irradiated up to the point in the close region of about 5 m forward from the lamp unit.
Furthermore, by way of setting the luminous intensity of each of the peaks in the first angle position higher than that of the peaks in the second angle position, it is possible to irradiate the lane marks along their longitudinal direction with relatively uniform illumination.
Recently, in lamp units for irradiating the point on the road ahead of a vehicle with a light beam a line segment light source that extends along the longitudinal axis has been increasingly used. In these lamps, if the lamp unit is viewed from behind, the light distribution pattern irradiated forward with a light beam from a region located upper right and lower left positions with respect to the center of the lamp unit is formed in accordance with an image that extends diagonally from the upper right to the lower left. The light distribution pattern irradiated forward with a light beam from the region located upper left position and lower right position with respect to the lamp unit is formed in accordance with the image that extends diagonally from the upper left position to the lower right position.
Accordingly, by way of setting so that the vehicle lamp irradiates a light beam leftward, when viewed from behind the lamp, from regions located at upper right position and/or lower left position with respect to the center of the lamp and also by way of setting so that the lamp irradiates a light beam rightward, when viewed from behind the lamp, from regions located at upper left position and/or lower right position with respect to the center of the lamp, then it is possible to efficiently irradiate the lane marks on left and right sides of the road ahead of the vehicle.
In the above, the description is made for a single vehicle lamp that irradiates the lane marks on both left and right sides of the road. However, the headlamps are generally mounted, respectively, on the left and right front sides of a four-wheeled vehicle. It is thus possible to design so that the respective lamp units independently irradiates the lane marks by way of an idea that the left and right pair of lamp comprise a vehicle lamp unit.
More specifically, the luminous intensity distribution of the light distribution pattern formed by the left lamp in lateral direction in the first angle position which is inclined downward at a predetermined angle with respect to the longitudinal axis passing through the center of the lamp is set to a luminous intensity distribution that has a peak on the left side with respect to the longitudinal axis of the lamp; and also the luminous intensity distribution of the light distribution pattern formed by the right lamp in lateral direction in the first angle position is set to a luminous intensity distribution that has a peak on the right side with respect to the longitudinal axis passing through the center of the lamp. This arrangement allows the left lamp to irradiate the left lane marks with the light beam, and the right lamp irradiates the right lane marks with the light beam. Therefore, it is possible to irradiate the left and right lane marks without deviating the light beam emitted forward from the respective lamp units with respect to the lateral direction. The lane marks, thus, can be irradiated further efficiently and precisely.
In this case also, it is preferable that the first angle position be set to be downwardly inclined at 4xc2x0 with respect to the longitudinal axis so that the lane marks can be irradiated more brightly without emitting great glare to the driver of the oncoming vehicle.
Also when such a vehicle lamp as described above is employed, the following arrangement can still be employed. The luminous intensity distribution of the light distribution pattern formed by the left lamp in lateral direction in the second angle position which is downwardly inclined at a predetermined angle with respect to the first angle position is set to a luminous intensity distribution having a peak on the left side of the longitudinal axis passing through the center of the left lamp, and the peak is positioned to the left of the peak in the first angle position; and in addition the luminous intensity distribution of the light distribution pattern formed by the right lamp in lateral direction in the second angle position is set to a luminous intensity distribution having a peak on the right side of the longitudinal axis passing through the center of the right lamp, and the peak is positioned to the right of the peak in the first angle position. This structure brightly irradiates the road surface ahead of the vehicle along the lane marks.
In this case also, by way of setting the second angle position to be inclined downward at 8xc2x0 with respect to the longitudinal axis, the lane marks can be reliably irradiated to the region as close as possible.
Furthermore, if the luminous intensity of each of the peaks in the first angle position is set higher than that of those peaks in the second angle position, the lane marks can be irradiated with relatively uniform illumination along the longitudinal direction.
Further, by way of setting so that the left lamp irradiates a light beam leftward, when viewed from behind the left lamp, from regions located at upper right position and/or lower left position with respect to the center of the left lamp; and by way of setting so that the right lamp irradiates a light beam rightward, when viewed from behind the right lamp, from regions located at upper left position and/or lower right position with respect to the center of the right lamp, it is possible to efficiently irradiate the road surface ahead of the vehicle along the lane marks.